A gray-colored soda lime glass (soda lime glass will be also simply referred to as glass) may be used as a window glass for a building, a vehicle, or the like. The gray-colored glass is required not only to be low in excitation purity (Pe) but also to be moderately low in visible light transmittance (Tv), low in solar direct transmittance (Te), and high in Tv/Te ratio. In addition, a gray glass in which an amber color has been reduced is preferred by customers.
In the gray-colored glass, various coloring components such as Se, Co, Fe, and Ni are used and combined depending on an expected color. For example, in order to obtain a bluish gray color, Fe (blue, yellow), Se (red) and Co (blue) can be added as coloring components. Of them, Se is an element which is often used for adjusting a color tone, but Se can be easily volatilized at a melting temperature of the glass. Therefore, ordinarily, only a small part of added Se remains in a final glass product (Non-Patent Literature 1).
Glasses described in Patent Literatures 1 to 4 have been known as glasses with low Pe.